1. Field of the Invention
The present invention relates to an interleaver for separating the wavelengths of light.
2. Related Background Art
An interleaver is for inputting a signal light with multiband (xcex1, xcex2, - - - , xcex2nxe2x88x921, xcex2n, - - - ) so as to separate into a signal light with a first wavelength group xcex91 (xcex1, xcex3, - - - , xcex2nxe2x88x921, - - - ) and a signal light with a second wavelength group xcex92 (xcex2, xcex4, - - - , xcex2n, - - - ), and is installed in a relay of an optical communication system, for example. For such an interleaver, various types have been proposed, such as one comprised of a polarization separation element, wavelength filter and polarization composing element, or one comprised of an optical system which constitutes a Mach-Zehnder interferometer. An interleaver comprised of an optical system which constitutes a Michelson interferometer is also possible.
However, in the case of the interleaver comprised of an optical system which constitutes a general Michelson interferometer, an input optical axis and one of the output optical axes exist on a same axis, so an optical circulator for branching the input light and the output light is required. This makes the interleaver expensive and makes the optical system in the interleaver complicated.
With the foregoing in view, it is an object of the present invention to solve the above problems, and to provide an interleaver which is inexpensive and with a less complex optical system.
An interleaver according to the present invention comprises an optical system having a first port, a second port, a third port, a half mirror, a first reflecting mirror, and a second reflecting mirror, wherein light which reaches from the first port to the half mirror is branched into two, and these lights are output to the first reflecting mirror and the second reflecting mirror respectively, light which is reflected by the first reflecting mirror and reaches the half mirror is branched into two, and these lights are output to the second port and the third port respectively, and light which is reflected by the second reflecting mirror and reaches the half mirror is branched into two, and these lights are output to the second port and the third port respectively.
It is preferable that in the optical system, the output optical axis from the half mirror to the first reflecting mirror and the reflected optical axis from the first reflecting mirror cross at a predetermined angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
It is also preferable that in the optical system, the input optical axis from the first port to the half mirror and at least one of the output optical axes from the half mirror to the second port and the third port cross with the branching face of the half mirror at a predetermined angle other than 45xc2x0, so that the output optical axis from the half mirror to the first reflecting mirror and the reflected optical axis from the first reflecting mirror cross at an angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
It is also preferable that in the optical system, the output optical axis to the first reflecting mirror crosses with the reflecting face of the first reflecting mirror at a predetermined angle other than 90xc2x0, and the output optical axis to the second reflecting mirror crosses with the reflecting face of the second reflecting mirror at a predetermined angle other than 90xc2x0, so that the output optical axis from the half mirror to the first reflecting mirror and the reflected optical axis from the first reflecting mirror cross at a predetermined angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
It is also preferable that in the optical system, the input optical axis from the first port to the half mirror and at least one of the output optical axes from the half mirror to the second port and the third port cross with the branching face of the half mirror at a predetermined angle other than 45xc2x0, the output optical axis to the first reflecting mirror crosses with the reflecting face of the first reflecting mirror at a predetermined angle other than 90xc2x0, and the output optical axis to the second reflecting mirror crosses with the reflecting face of the second reflecting mirror at a predetermined angle other than 90xc2x0, so that the output optical axis from the half mirror to the first reflecting mirror and the reflected optical axis from the first reflecting mirror cross at a predetermined angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
It is also preferable that the interleaver further comprises optical axis correction means for paralleling the input optical axis from the first port and the output optical axis to the second port.
It is also preferable that the optical axis correction means further comprises a prism for converting a state where the input optical axis from the first port and the output optical axis to the second port cross at a predetermined angle into a state where the input optical axis and the output optical axis are parallel.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
An interleaver according to the present invention, further comprises a polarization separation element which is installed between the first port of the optical system and the half mirror for separating the light which reaches from the first port into two lights having polarization planes perpendicular to each other, and outputting the separated lights to different optical paths respectively.
It is preferable that the interleaver further comprises a polarization plane paralleling element which is installed between the polarization separation element and the half mirror of the optical system, inputs two lights which are output from the polarization separation element and have the polarization planes perpendicular to each other, parallels the polarization planes of the respective lights, and outputs the paralleled lights to the half mirror respectively.
It is also preferable that the interleaver further comprises a polarization plane orthogonalizing element which is installed between the half mirror and the second port of the optical system, inputs two lights which reach from the half mirror and have polarization planes parallel to each other, orthogonalizes the polarization planes of the respective lights, and outputs the orthogonalized lights to the second port respectively.
It is also preferable that the interleaver further comprises a polarization combining element which is installed between the polarization plane orthogonalizing element and the second port of the optical system, inputs two lights which are output from the polarization plane orthogonalizing element and have the polarization planes perpendicular to each other, combines these two lights, and outputs them to the second port.
It is also preferable that the interleaver further comprises a polarization plane orthogonalizing element which is installed between the half mirror and the third port of the optical system, inputs two lights which reach from the half mirror and have polarization planes parallel to each other, orthogonalizes the polarization planes of the respective light, and outputs the orthogonalized lights to the third port respectively.
It is also preferable that the interleaver further comprises a polarization combining element which is installed between the polarization plane orthogonalizing element and the third port of the optical system, inputs two lights which are output from the polarization plane orthogonalizing element and have the polarization planes perpendicular to each other, combines these two lights, and outputs them to the third port.
It is also preferable that the optical system outputs one of the two lights, which are output from the polarization separation element and have polarization planes perpendicular to each other, to the second port, and outputs the other light to the third port.
An interleaver according to the present invention further comprises a polarization separation element which is installed between the second port of the optical system and the half mirror for separating light which reaches from the half mirror into two lights having polarization planes perpendicular to each other, and outputting one of the separated lights to the second port; and a polarization separation element which is installed between the third port of the optical system and the half mirror for separating light which reaches from the half mirror into two lights having polarization planes perpendicular to each other, and outputting the light having a polarization plane, which is perpendicular to the polarization plane of the light to be output to the second port, to the third port.
It is preferable that in the optical system, the output optical axis from the half mirror to the first reflecting mirror and the reflected optical axis from the first reflecting mirror cross at a predetermined angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
Is also preferable that in the optical system, the input optical axis from the first port to the half mirror and at least one of the output optical axes from the half mirror to the second port and the third port cross with the branching face of the half mirror at a predetermined angle other than 45xc2x0, so that the output optical axis from the half mirror to the first reflecting mirror and the reflected optical axis from the first reflecting mirror cross at a predetermined angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
It is also preferable that in the optical system, the output optical axis to the first reflecting mirror crosses with the reflecting face of the first reflecting mirror at a predetermined angle other than 90xc2x0, and the output optical axis to the second reflecting mirror crosses with the reflecting face of the second reflecting mirror at a predetermined angle other than 90xc2x0, so that the output optical axis from the half mirror to the first reflecting mirror and the reflecting optical axis from the first reflecting mirror cross at a predetermined angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
It is also preferable that in the optical system, the input optical axis from the first port to the half mirror and at least one of the output optical axes from the half mirror to the second port and the third port cross with the branching face of the half mirror at a predetermined angle other than 45xc2x0, the output optical axis to the first reflecting mirror crosses with the reflecting face of the first reflecting mirror at a predetermined angle other than 90xc2x0, and the output optical axis to the second reflecting mirror crosses with the reflecting face of the second reflecting mirror at a predetermined angle other than 90xc2x0, so that the output optical axis from the half mirror to the first reflecting mirror and the reflected optical axis from the first reflecting mirror cross at a predetermined angle greater than 0xc2x0, and the output optical axis from the half mirror to the second reflecting mirror and the reflected optical axis from the second reflecting mirror cross at a predetermined angle greater than 0xc2x0.
It is also preferable that the interleaver further comprises optical axis correction means for paralleling the input optical axis from the first port and the output optical axis to the second port.
It is also preferable that the optical axis correction means further comprises a prism for converting a state where the input optical axis from the first port and the output axis to the second port cross at a predetermined angle into a state where the input optical axis and the output optical axis are parallel.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.